code: def build_mean_function():
      tf.keras.backend.set_floatx("float64")
      assert default_float() == np.float64
  
      inputs = tf.keras.layers.Input(shape=(1,))
      x = tf.keras.layers.Dense(64, activation="relu")(inputs)
      x = tf.keras.layers.Dense(64, activation="relu")(x)
      outputs = tf.keras.layers.Dense(1)(x)
      return tf.keras.Model(inputs=inputs, outputs=outputs)
  
file_path: GPflow/notebooks/tailor/external-mean-function.pct.py
imports: import matplotlib.pyplot
  import numpy
  import tensorflow
  import gpflow
  from gpflow.ci_utils import reduce_in_tests
  from gpflow.kernels import RBF
  from gpflow.models import GPR
  from gpflow.config import default_float
  from gpflow import set_trainable
  import time
label_desc: Use image node_id 3 for calling a global function with example usage: build_mean_function() and returns: tf